1. Field of the Invention
The present invention generally relates to a laminate circuit board with a multi-layer circuit structure, and more specifically to a nanometer plating layer over a metal circuit layer without reserving circuit width for compensation.
2. The Prior Arts
Please refer to FIG. 1. The laminate circuit board with the multi-layer circuit structure in the prior arts generally comprises a substrate 10, a circuit metal layer 25 and a cover layer 30, as shown in FIG. 1. The substrate 10 has a rough upper surface 15, on which the circuit metal layer 25 made of at least one of copper, aluminum, silver and gold is formed. The cover layer 30 made of a binder or a solder resist is formed to cover the circuit metal layer 25. Since the circuit metal layer 25 and cover layer 30 are made of different materials, the outer surface of the circuit metal layer 25 needs to be roughened to form a roughened outer surface 27 by chemical, mechanical or plasma treatment so as to increase the surface friction coefficient and avoid peeling off. Thus, the junction property is improved by the roughened outer surface 27.
However, one of the shortcomings of the circuit metal layer 25 with the roughened outer surface 27 in the prior arts is that it is necessary to reserve some circuit width to compensate the loss due to the roughening process, and the design of the circuit is thus greatly constrained, especially for much denser circuit in the current application. Therefore, it needs a laminate circuit board with a multi-layer circuit structure with reduced compensation for circuit width to increase the density of the circuit.